Control apparatus



March 23, 1948. E. c. STRONG ET AL CONTROL APPARATUS Filed Nov. 17, 19432 Sheets-Sheet l INVENTORS Elbia C. Strong Leverett MClark.

BY Q

ATTORNEY March 23, 1948. c, STRONG ET AL 2,438,352

CONTROL APPARATUS Filed Nov. 17, 1943 2 Sheets-Sheet 2 CONTROL MOTOR.

u 4 UPPER LlMlT 5W lTCH SW ITCH PROTECTIVE I INVENTORSv Elbie CStTong134 Levemrt M.Clarf P BY '1 B M I )QAi-Uf w l l'l h 1: ATTORNEY PatentedMar. 23, 1948 UNITED STATES PATENT OFFICE CONTROL APPARATUS ApplicationNovember 17, 1943, Serial No. 510,590

5 Claims. 1

This invention relates to apparatus for controlling loads, strains andmovements in machine and structural members and has for an object theprovision of improvements in this art.

Parts and members of machines and structures are designed to carry loadsand to Withstand strains, movements, and forces. Such members are attimes subjected to loads or strains in excess of those Which they weredesigned to withstand, overloads are undesirable and many times causefailure of members. It is often necessary to provide means of preventingoverloading of members of machines or structures. It is common practiceto provide means to indicate the magnitude of power input to or loadsapplied to a machine or structure as a whole. Common means may be meterssuch as wattmeters, pressure gages and overload devices in the powersupply line itself. Meters serve only to indicate the magnitudes ofloads that have been applied but not to limit the load to a desirable orsafe value. Devices in the power supply lines serve as protectors to theprime mover itself rather than to the machine or structure. In manycases the machine or structure as a Whole may not be overloaded, but oneor more individual members may be. The type of protection which isneeded is one that will control or limit the loads, strains or movementsin or on the individual member.

One of the objects of this invention is to pr vide a means ofcontrolling or limiting the loads on a member of a machine or structureby utilizing the strain in the member itself due to the loads imposedupon it. A device which accomplishes this purpose will be describedhereafter. Such a device may be used on one or more members of a machineor structure or may be used on the machine or structure as a whole.Another object of this invention is to provide means for controlling orlimiting movements and displace ments in equipment as distinguished fromloads or strains. This object may be accomplished by utilizing thestrain in the member subject to movement and by employing auxiliarydevices such as relays, switches and motors.

One application of the invention is to the control of aircraft wingflaps in take-oil and landing. In airplane operation, particularly onairfields with runways of limited length, it is important to increasethe lift during take-off or landing when lower speeds prevail, The pilotmay set the flaps manually to accomplish this but it is desirable torelieve him of constant attention to their operation and to avoidexcessive strains upon the flap operating mechanism. The

present invention provides apparatus which can be set into action by thepilot and which will thereafter operate automatically to hold the flapsin the extreme position for a predetermined max imum strain on theiroperating mechanism. It may be desirable to provide one condition fortake-off and another for landing, it being usual with some aircraft, forexample, to take off at seventy miles per hour and to land at one huh--dred miles per hour. Accordingly the invention provides means forselectively operating at a plurality of strain limits. The invention maof course, have many other applications for selective control wheredifferential movements are encountered.

One of the particular objects of the invention is to provide an improveddevice for registering distortion in a stressed member and toautomatically reduce the stress to safe limits.

Another object is to provide a plurality of selective limit controls fordififerent conditions.

Another object is to provide simple and slicetive mechanical switchoperating means responsive to movements of a stressed member.

The above-mentioned and other objects Will be apparent from thefollowing description of an exemplary embodiment of the invention,reference being made to the accompanying drawings, wherein:

Fig. l is a schematic plan View of the invention applied to the controlof airplane Wing flaps;

Fig, 2 is a vertical elevation of the switch operating device applied toa load carrying member such as the push-full fiap operating tube or redof an airplane;

Fig. 3 is a horizontal section taken on the line 3-3 of Fig. 2;

Fig. is an inside elevation;

Fig. 5 is a transverse section on the line 55 of Fig, 2; and

Fig, 6 is a wiring diagram of the installation shown in Fig. 1.

As applied to the airplane of Fig. l, th flaps ill of the wings I! areoperated through pushpull rods l 2 from motors M. up by push and down bypull. The are, of course. 1 iced by air pressure when the airplane is inflight. One of the push-pull rods is provided with a device M accordingto the present invention which. through means to be described controlsin part the operation of the motors M, the entire mechanism being underthe supervision of the pilot through a selective switch on the controlpanel l5. The pilot may also selectively operate the flaps independentlyof the motors and strain sensitive means as by a crank l6 and flexibleshafting l! suitably connected to the push-pull rods. Certain junctionboxes l8, I9, 20 and gear boxes 2|, 22, 23 are shown in Fig. l but needno further attention.

6 illustrates the control circuit. The motor M when set into operation,if not otherwise halted, will be stopped in limiting positions of theflap by an upper limit switch Ll or a lower limit switch L2. The motoris powered from any suitable current supply, as for example a battery B,a master cut out switch (not shown) being employed to take the flapsfrom under the control of the motor when desired. The flaps may still beadjusted or operated by the hand crank it.

When the motor is in circuit it is controlled by a relay R which isconstantly urged to flap lowering contact position by a spring '20 andmoved in the opposite or flap raising position when desired by asolenoid 2i. The relay coil, battery and motor are grounded at G.

Means are provided for operating the relay at one or more predeterminedstrain points of the push-pull rod l2 or independently of any stress inthe rod. This means comprises a pilots control switch P having contactsPl, P2, P3 and P 5, respectively, for take-oii, raise flaps, oil, andland. The contacts PI and Pi areconnected to the relay B through limitswitches SI and S2, respectively, and the contact P2 is connected to therelay directly. A series protective circuit 23, including a resistanceand a, condenser, is placed in series with the relay coil in parallelwith the circuit through the limit switches to damp possible chatter andarcing of the switch contacts.

The switches Si, S2 are secured as companion control elements on thepush-pull rod l2. TheS may be of different characteristics but as shownmay be of identical characteristics with difierent settings. They arepreferably plunger toggle throw switches of the Microswitch type whichoperate at a given point with very slight force and displacement.

The switches SI and S2 are mounted in a sealed box 25 which is rigidlysecured to the push-pull rod l2 by clamps 26. An operating rod '27enters the box 25 through a felt-sealed opening at one end and isattached at its outer end to the pushpull rod 12 by a clamp 28. Theoperating rod may be made of any suitable material, preferably the sameas the push-pull rod, and its length is determined by the sensitivitydesired.

The rod 27 operates the switches SI, S2 through bell-crank levers 30, 3!pivoted on eccentric adjusted shafts 32, 33, one arm 38a or am of eachcrank being provided with a rounded projection 30b or 3Ib which engagesa wear plate 34 secured on the end of the rod 21 and the other arm beingpulled downward by a spring 35. The springs close the switches. Theeccentric shafts 32, 33 are adjusted from the outside of the casing andare held in adjusted positions by locknuts 36. The eccentric shafts 32and 33 are adjusted in such a manner that there is required a greatermovement of bell-crank lever 3! to operate switch 8-2 for landing thanis required for bell-crank 39 to operate switch S-l for take-oil. Inthis manner of operation there is provided flap elevation at lowertake-ofi speeds than for landing speeds. Comparative strain may, forexample, correspond respectively to 2500 pounds take-off and 5000 poundslanding. The switches are provided with leads d passing out of the boxthrough a sealed bushing 4 or socket fitting 4!. A preferred setting isto have the projections of the bell-crank arms in the same plane of theend of the plate 3d and at the mid-height of the rod 2? when there is nostrain in the push-pull rod l2 and the eccentrics are in the sameadjusted positions. Then one or both of the eccentrics is adjusted untilits switch operates at the desired load point. It will be noted that thebell-cranks are brought close together at their pivot shafts to bringthe rod-engaging arms close together and in symmetrical relation to thevertical axial plane of the rod '22.

In operation, when the switch P is at the off position P3 the relay isbiased by the spring 2% in the direction to maintain the flaps in theirlowermost position. When the switch P is at the raised flaps positionP2, th relay coil 2! is continuously energized and the flaps aremaintained in their raised position, controlled by the upper limitswitch Ll. This is the normal flight condition.

When the switch P is at the take-off position Pl, the switch SI is incircuit. and when the push-pull rod l2 is elongated by a predeterminedamount, say when the pull in the rod is 2500 p. s. 1., the plate 3 5 ofthe control rod Z'l moves back sufficiently to permit the spring to movethe bell-crank lever 35 and operate the switch SI. Through relay R. thisoperates the motor M to raise the flaps and relieve the tension in thepush-pull rod 2?. This opens switch Si, allows spring 28 to operate therelay in the reverse direction and operate the motor to lower the flapsagain. This balancing adjustment continues as long as the predeterminedstrain is present, though it may mean many different settings of theflaps and when the strain is continuously under the predetermined amountthe motor operates until the lower limit switch is operated with theflaps in their fully lowered position. If the strain continues to riseabove the predetermined point, on the other hand, the flaps will becarried to their fully raised position.

When the switch P is moved to the land position, the switch S2 is placedin circuit with the relay and the same operation is realized as withswitch Si but at a diiierent predetermined strain value.

There may be one, two or any desired number of switches mounted togetherto serve various purposes and to operate at various loadings. Someapplications may bethe following:

Overload prevention: In aircraft cables, cables of cranes, hoists, towlines and structural members of cranes, hoists, and power presses.

Minimum and/or maximum loads or stresses:

During pressing operations such as installation of tires, gears, wheels.

Minimum and/or maximum loads or stresses:

In members of machines, buildings, and structures of all kinds includingconcrete, steel, or other materials.

Warning signals: On bridge members or cables, building members and otherstructures and tow lines.

Limiting of movements or displacements: In electric and power lines,cables and wiring in aircraft, and many types of sagging or taut wiresand cables.

Instead of or in addition to controlling loads the apparatus may measureand indicate loads or strains by the introduction f suitable indicators.

It will be evident that the invention has many applications other thanthat described. Also that it may have other embodiments within thelimits of the prior art and the scope of the subjoined claims.

What is claimed is:

1. Apparatus for measuring and controlling loads, movements and thelike, comprising in combination, a push-pull rod, a switch box mountedon said push-pull rod, a control rod secured to said push-pull rod at aspaced point from said switch box and having its free end extending intosaid box, and a plurality of switches in said switch box movedconcurrently by said control rod but having effective operation atdifferent positions of said control rod, means for changing the load onsaid push-pull rod, and means for selectively operating said loadchanging means through one of said switches.

2. Apparatus for measuring and controlling loads, movements and thelike, comprising in combination, a push-pull rod, a switch box andcontrol rod secured at spaced points along said push-pull rod; aplurality of plunger toggle switches mounted in said switch box withtheir plungers at right angles to said rods, bell-crank levers mountedin said switch box on adjustable pivot shafts, means for actuating saidbell-crank levers together by said control rod by change in length ofsaid push-pull rod, springs for moving the levers in the other directionto operate said switches, the switches being arranged to operate atdifferent load limits, and means for adjusting the operating position ofsaid levers.

3. Apparatus for measuring and controlling loads, movements and thelike, comprising in combination, a load-carrying member, a plurality ofswitches mounted thereon at a first point, a control rod mounted on saidmember at a second point, and means cooperating with the free end ofsaid rod and with said switches for operating said switches at differentamounts of movement of said rod.

4. Apparatus as set forth in claim 3, in which said means includesbell-crank levers each connected to a switch and all operativelyassociated with the end of said rod, and means for adjusting thefulcrums of said cranks individually.

5. Apparatus for controlling loads comprising load means, pluralswitches, a rod connection between said load means and switchessusceptible to load strain variation, control connections between saidsaid switches and rod connection whereby said switches are actuated onlyon predetermined conditions of load strain, and adjustment means foraltering the time of actuation of each operated switch.

ELBIE C. STRONG. LEVERETT M. CLARK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,440,610 Kupetz Jan. 2, 19232,237,170 Williamson Apr. 1, 1941 2,362,343 Bath Nov. '7, 1944

